Hi,

How can I rotate a bitmap 90? counterclockwise ?

Alternatively, how can I read/write the pixels in the bitmap ? I found ReadChannels/WriteChannels from RawImage, but they use a strange kind of position object which I don't understand :(

(an alternate answer is to implement rotated fonts in GTK1 ;))

Michael.

2008/10/27 Michael Van Canneyt :

Hi, How can I rotate a bitmap 90? counterclockwise ?

Wouldn't a rotation matrix do the trick? I remember the old fpGUI code (gfxbase.pas) unit used a 3x3 matrix to do translations and scalations calculations. I would imagine the same could be applied for rotation.

Wikipedia has some articles on rotation matrix, but the formulas look scary. ;-) Google revealed a lot of links on rotation matrix.

Alternatively, how can I read/write the pixels in the bitmap ?

The TFPCustomCanvas.Colors[] array?

Regards,
- Graeme -

_______________________________________________
fpGUI - a cross-platform Free Pascal GUI toolkit
http://opensoft.homeip.net/fpgui/

2008/10/27 Michael Van Canneyt :

Hi, How can I rotate a bitmap 90? counterclockwise ?

To save you the trouble... :-)

http://www.efg2.com/Lab/ImageProcessing/RotateScanline.htm http://www.delphi-central.com/tutorials/RotateBitmapBitBlt.aspx http://delphi.about.com/cs/adptips2001/a/bltip1201_4.htm

Regards,
- Graeme -

_______________________________________________
fpGUI - a cross-platform Free Pascal GUI toolkit
http://opensoft.homeip.net/fpgui/

2008/10/27 Michael Van Canneyt :

2008/10/27 Michael Van Canneyt :

Maybe the lazintf example
(http://svn.freepascal.org/svn/lazarus/trunk/examples/lazintfimage/) can help. It rotates an image.

Vincent

Try
https://lazarus-ccr.svn.sourceforge.net/svnroot/lazarus-ccr/components/gradcontrols/src/urotatebitmap.pas

Attached is a test example.

Luiz
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Thank you, but I already saw those prior to asking my questions. None of the techniques described there work in Lazarus.

Michael.

Exactly what I needed. TLazIntfImage is the missing link :-)

Thanks to everyone for the links !

Michael.

I had a similar problem... Eventually I moved on to GLscene...

Though obviously it's probably not at all what you want to do, but it's pretty easy to rotate things there. :-)

obj.rollangle := obj.rollangle + 90;

You can use an orthogonal camera if you don't want / need the perspective.

You can even let it "slowly" rotate using a cadencer, but let's not jump the gun here.

Regards,
-Reenen

2008/10/27 Michael Van Canneyt

All I need is to display a text at a 90? angle. Since GTK 1 doesn't support rotated text (hint hint), I draw the text on a bitmap, rotate that 90 degrees and display the bitmap, when I detect GTK1 as a widget set :-)

Requiring OpenGL for this would be slightly over the top, I'm sure you'll agree :-)

Michael.

Take a look at the unit i pointed. It has a class that does specifically this.

Luiz

Indeed it does. Thanks for the hint.

I'll use my implementation since it uses the built-in rotated font if available. (and it was ready anyway :-) )

Michael.